1991 Fiscal Year Final Research Report Summary
Research on Trace Element Contents in Granitoids
| Project/Area Number |
01540667
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| Research Category |
Grant-in-Aid for General Scientific Research (C)
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| Allocation Type | Single-year Grants |
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| Research Field |
鉱物学(含岩石・鉱床学)
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| Research Institution | Kumamoto University |
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Principal Investigator |
TSUSUE Akio Kumamoto Univ. Prof., 理学部, 教授 (20011512)
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| Co-Investigator(Kenkyū-buntansha) |
YOKOSE Hisayoshi Kumamoto Univ. Res. Fellow, 理学部, 助手 (50230644)
MIZUTA Toshio Akita Univ. Assoc. Prof., 鉱山学部, 助教授 (80094051)
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| Project Period (FY) |
1989 – 1991
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| Keywords | Outer Zone of Southwest Japan / I-type granitoids / S-type granitoids / Mineral assemblage / Butsuzo Tectonic Line / Middle Miocene / Omine district, Kii peninsula / Takatsukiyama |
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| Research Abstract |
The Outer Zone granitoids have been divided into two groups, namely, 1- and S-types. The granitoids occurring in the northern part of the Butsuzo Tectonic Line of the Outer Zone of Southwest Japan tend to have I-type characteristics, and S-type granitoids are generally restricted to the south. In addition to I- and S-type discrimination, some geochemical variations have been observed : K_2O, total Fe and normat6ive corundum increase toward the pacific side, while Fe_2O_3/FeO* (total Fe as FeO) ratio decreases. In this report we intend to report mineral assemblages of granitoids of the Omine district in the Kii peninsula and Takatsukiyama pluton in Shikoku. In the Omine district, granitoids are intermittently found along the trend of NS about 40 km long. The boundary of I- and S-type granitoids is located just about the Butsuzo Tectonic Line. The presence of amphibole is the characteristics of mineral assemblage of I-type granitoids, while the absence of amphibole and occasional presence of cordierite or garnet are the characteristics of S-type granitoids. The IS-type granitoids are found as separated plutons in the Omine district. The Takatsukiyarna pluton in Shikoku is located at 10 km south of the Butsuzo Tectonic Line. The pluton intruded into the Lower Shimanoto Supergroup of the Late Cretaceous age Depending on the field occurrence and mineral assembllage, the Takatsukiyama granitoids have been divided into three major petrographic types, namely, B-, W-C, W-A types. The B-type granitoid is found as a small ovoid body, 1 km X 0.5 km size, completely enclosed in the central part of the w-type body. The B- and W-A type granitoids belong to I-type, while the W-C type granitoids belong to S-type. The presence of the Land S-type granitoids within a single pluton is a characteristics of the pluton, and that must be the problem to solve.
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